How they used torpedoes in World War I?

they used controllers that were in the submarine and they watched to see where it was headed with a spy glass that they had invented its kind of like the one we use today.

In WW 1 a torpedo was essentially a complex clockwork mechanism that was principally intended to get it to run in a straight line until it hit something, preferably the target. But much like a bullet fried from a gun, once fired it could not be controlled.

Ideally it would simply run in a straight line and explode upon impact with the target ship.